The invention relates to a method of drying objects having been surface treated for depositing thereupon a protective layer such as that of a varnish, paint or another coating material, or for providing thereon such a protective layer otherwise, especially in a chemical way.
The method comprises the steps of placing said objects into a closed space, contacting them inside said space with a stream of a heated gaseous medium, such as for instance hot air, which gaseous medium will be referred to hereinafter as gas only. By the gas heat, evaporation is provoked from the objects of the moisture their surface layer contains. Thus especially solvents and other ingredients of the varnish, paint or coating get vaporized. Then, the drying gas is discharged from said closed space and the heat content thereof is reutilized for further drying. This then may be done by reintroducing said discharged gas into the drying space. However, it also is possible to thus reutilize a portion only of this discharged gas and to release the other portion, together with the evaporates and/or products of chemical processes occurred in said closed space into the ambient atmosphere.
It has been known heretofore to expose the so surface treated objects to a hot gas in a closed space, such as a drying chamber, for causing an accelerated drying of such objects by evaporating from their surface the moisture present in the layers formed thereupon by for instance varnishing, painting and other coating processing and for having the products of chemical processes occurring in the closed space admixed with the hot gas, then exhausting the gas charged with the vapors and/or chemical gaseous products and releasing this so-charged gas into the surrounding atmosphere. There also have been known various devices designed for carrying out such methods, i.e. devices having a closed drying chamber equipped with heated gas supply, exhaust and release conduits.
The known methods have the disadvantages that no efficient provision is made for cleansing the effluent gas leaving the drying space before releasing it into the atmosphere, in order to separate from this released effluent gas harmful and often toxic substances which are hazardous for human health, in particular that of the process operators and all persons arriving to or present in the shop or place where the drying process is performed.